I’m keeping this short to put a very simple idea into your head. Because
of the way the Democratic Party voting calendar is structured this
year, Clinton’s largest lead will occur on March 15. After that, most of Sanders’ strongest states will vote.
What this means is simple:

Hillary Clinton will grow her lead until the March 15 states have voted.

Bernie Sanders will erase that lead — partly or completely — after March 15.

How much of Clinton’s lead he will erase depends on your not buying what the media is selling — that the contest is over.

In most scenarios where Sanders wins, he doesn’t retake the lead
until June 7, when five states including California cast their ballots.

March 15 is the Ides of March; a good way to remember the date. The
message — gear up for a battle after the Ides of March, and don’t let
the establishment media tell you what to think. They won’t be right
until the last state has voted.
If you want to stop reading here, this is all you need to know.The Data
Now the data. One of the best data-stitians I’ve come across is a
diarist at Daily Kos named MattTX. Matt is very good, professionally
good, at this stuff. In a long, carefully-reasoned diary, “How Bernie Sanders can win the Democratic nomination,”
he lays out six scenarios for the race, in five of which Bernie Sanders
wins the nomination (the other is a current baseline with no momentum).
He presents them in a parallel fashion, and each presentation differs
only in changing a small set of assumptions. Once you understand how to
read the first one, you can read the others easily.
The first three scenarios are “static” — they assume that the
national polling remains fixed throughout the race. He then runs the
numbers on each state race for the following assumptions:

Then he looks at what “momentum” looks like in a number of recent
presidential contests (it actually can take a number of shapes) and
chooses a momentum pattern associated with Obama’s win over Clinton in
2008. (Click here to see that chart.)
His final three scenarios are “dynamic” variations of his static
ones, with shifting momentum off the current baseline. In each of these,
Sanders wins, each time overcoming the bulge in the Clinton lead that
comes on March 15. In the narrowest of these winning scenarios, the
March 15 bulge is quite large, +184 delegates for Clinton.
Note that the data in Matt’s piece was run prior to South Carolina’s
results, so Sanders has some additional ground to make up. Still,
Sanders is right to “take it to the convention.” Most of his strength
comes after most of Clinton’s, and Sanders could easily surprise in his
states, just as Clinton will surprise in some of hers. Again, we won’t
know who has the lead for good until after California and four
additional states vote in early June.Bottom line — What looks bad for Sanders supporters on March 1
will look worse a few weeks later. But stay heartened. Whatever the
result through March, this isn’t over until June, after Sanders’ best
states have voted as well.
(Blue America has endorsed Bernie Sanders for president. If you’d like to help out, go here; you can adjust the split any way you like at the link. If you’d like to “phone-bank for Bernie,” go here. You can volunteer in other ways by going here. And thanks!)